Selector mechanism



Feb. 13, 1962 H. F. WELSH ETAL 3,

SELECTOR MECHANISMS Filed April 27, 1956 3 Sheets-Sheet 1 [8 FIG. IA. 8|T Defenf Arm Oulpuf Sheff Inner Wrap Spring 85 I Defenf Arm FIG. IC.

INVENTORS H. E WELSH BY N.J. APPLETON M. SILVERB ERG )(Maz' A GENT Feb.13, 1962 H. F. WELSH ETAL 3,021,512

SELECTOR MECHANISMS Filed April 27, 1956 3 Sheets-Sheet 2 Feb. 13, 1962H. F. WELSH ETAL 3,021,512

SELECTOR MECHANISMS Filed April 27, 1956 3 Sheets-Sheet 3 TransducerCarriage F IG. 3.

INVENTORS HIF. WELSH BY N. J. APPLETON M. SILVERBERG AGENT United StatesPatent @fifice 3,021,512 Patented Feb. 13, 1962 3,021,512 SELECTORMECHANISM Herbert Frazer Welsh and Norman J. Appleton, Philadelphia, andMorton Silverberg, Elklns Bark, Pa, assignors to Sperry RandCorporation, New York, N.Y., a corporation of Delaware Filed Apr. 27,1956, Ser. No. 581,235 23 Claims. (Cl. 340174.1)

The present invention relates to mechanisms for selectively positioninga Work piece at one of a plurality of possible locations in response tocoding signals; and is more particularly concerned with such selectormechanisms capable of utilization in digital computation systems, forinstance as a portion of a disk-type magnetic memory.

It is often desired, in various mechanical structures, to position awork piece between any one of a number of stations. In the past, suchpositioning mechanisms have, for the most part, employedservo-mechanisms for moving the said work piece between individualstations, and feedback means have been employed in combination with suchservo-mechanisms to signal when the work piece has arrived at thedesired location so as to deenergize the servo-mechanism and to causethe work piece to come to a stop. Other types of mechanisms known in theart for selectively positioning work pieces have often comprisedinterposer devices whereby the work piece is merely moved toward adesired position and is then forcibly brought to a stop by theinterposition of fixed stops serving to halt the work piece at thedesired position.

Each of these known types of selector mechanism has been subject to thedisadvantage that the resulting structure is relatively complex andcostly in construction; or that in the alternative, the device is somassive in character that selection is relatively slow and imposessubstantial physical strain upon the work piece, thereby raising thepossibility of operating failures with the attendant cost ofmaintenance.

The present invention serves to obviate the foregoing difficulties and,in essence, provides mechanisms which, without inverse feedbacktechniques or stops, may directly position a work piece into any one ofa plurality of digitally determined positions in response to a digitalinput code. The devices of the present invention find utility in digitalcomputation devices wherein it is desired to physically position a workpiece at one of a plurality of possible locations in response to aunique digital input code; and the work piece may comprise, for instancea magnetic transducer selectively positioned at one of a plurality ofstorage or pickup locations adjacent a magnetic storage surface. In thislatter respect, reference is made, for instance, to the copendingapplication of J. P. Eckert, et 2.1., Serial No. 485,746, filed February2, 1955, for Reading Apparatus, which discloses a disk-type memorycomprising a plurality of disk-like storage surfaces cooperating withwriting and detection means for the selective storage and reading ofinformation. The present application may be considered to providepossible selectors for the variable positioning of the writing anddetection means with respect to such disk-like memory surfaces.

In accordance with the present invention, the foregoing selectivepositioning of a work piece may be effected by coupling the said workpiece (e.g. a magnetic transducer) to an elongated cable, which cable inturn rides on a plurality of individually movable pulley devices and thesaid pulley devices may in turn be variably displaced in response toactuator means. By proper selection of the pulleys moved, as well as byappropriate preselection of the amount each pulley can move, the cablemay be selectively translated with respect to a plurality of stations(e.g. the magnetic records of a disk file) thereby to selectively movethe aforesaid work piece to a predetermined one of these stations. Ageneral system of this type is described in more detail, for instance,in US. Patent No. 1,139,972 to C'. J. Henschel and C. Messick.

In accordance with one embodiment of the present invention, the cableemployed may be fixed at at least one of its ends to a stationaryreference structure whereby the work piece may be selectively translatedin a single plane. In accordance with a further embodiment of thepresent invention, however, the cable may be affixed at at least one ofits ends to a movable reference structure whereby the system comprises adifierential selector mechanism capable of relative movement withrespect to two orthogonal planes. This latter embodiment of the presentinvention finds particular utility in the disk-type memory discussedpreviously, wherein it is desired first to move with respect to theover-all memory thereby to preselect a particular memory disk for thereading or writing of information thereon, and it is thereafter desiredto variably displace the reading or writing mechanism to one of aplurality of desired locations on the said selected disk. Each of theforegoing embodiments may, as will be described, employ various typcs ofpulse or signal responsive actuators, and a preferred form of theinvention utilizes selectively actuated Wrap spring clutches of noveldesign.

It is accordingly an object of the present invention to provide noveland improved selector mechanisms.

A further object of the present invention resides in improved mechanismsadapted to selectively position a work piece in response to a digitalinput code.

Still another object of the present invention resides in the provisionof novel selector mechanisms which need not employ feedback techniquesor stop mechanisms for selectively positioning a work piece, such as atransducer, at one of a plurality of work stations.

A further object of the present invention resides in the provision of adifferential selector mechanism wherein a work piece may be selectivelymoved in a first direction of operation without disturbing the positionof the said work piece with respect to a moving work station; andwherein the work piece may be selectively positioned at one of aplurality of work stations in a second direction of operation inresponse to a predetermined electrical signal input.

Another object of the present invention resides in the provision of anovel memory system wherein a magnetic transducer may be selectivelypositioned with respect to a magnetic storage surface in response to adigital input signal.

A further object of the present invention resides in the provision ofnovel selector mechanisms which are simpler in construction and morerugged in configuration than those known heretofore.

A further object of the present invention resides in the provision ofnovel selector mechanisms capable of more rapid and more efficientoperation than has been the case in the past.

Another object of the present invention resides in the provision of anovel selector mechanism employing a plurality of differentlycode-Weighted wrap spring clutches for selectively positioning a workpiece.

A still further object of the present invention resides in the provisionof a novel transducer positioning device for use in a disk-file memorysystem.

Another object of the present invention resides in the provision of animproved random access memory system capable of more rapid utilizationthan has been the case heretofore.

The foregoing objects, advantages, construction and operation of thepresent invention will become more readily apparent from the followingdescription and accompanying drawings, in which:

FIGURE 1A illustrates an improved wrap spring clutch constructed inaccordance with the present invention.

FIGURE 13 is a view taken on line B-B of FIGURE 1A.

FIGURE 1C illustrates an alternative ratchet and stop mechanism for awrap spring clutch such as may be employed in the present invention. I

FIGURE 11) illustrates a further portion of another alternative form ofwrap spring clutch such as may be employed in the present invention.

FIGURE 2 is a diagram of a selector mechanism utilizing wrapspringclutches of the type illustrated in FIGURE 1A; and

FIGURE 3 is a diagrammatic representation of a differential selectormechanism constructed in accordance with the present invention.

In the devices of the prior art, many forms of actuating members havebeen used. One such actuating mem her is the solenoid, and this has beenvery popular in de vices of the type described above. However, it hasbeen found that in servo-positioning systems, a preferred actuator takesthe form of 180 revolution clutches, and the elements to be moved, suchas the above mentioned rotatable pulleys, are eccentrically mounted onan output shaft of such half-revolution clutches for moving the saidpulleys to their said binary positions, thereby to alter the effectivelength of cable and the effective position of the work piece ortransducer.

Before proceeding with the detailed discussion of the present invention,it should be not that a 180 clutch is one which, upon being pulsed withthe proper signal, proceeds to rotate from one fixed position to anotherposition 180 away. Attached fully rotating pulleys, eccentric to theaxis of rotation of the clutch, will therefore displace through adistance equal to twice the eccentricity. The output motion imparted tothe cable, due to each clutch, is basically sinusoidal; and if theclutches are started at the same time and have the same r.p.m., the fulloutput is basically sinusoidal. This means that the output is started atmaximum acceleration and zero velocity, is then brought up to maximumvelocity and zero acceleration at a point near the center of the stroke;and is then brought to a stop with maximum acceleration and minimumvelocity at the end of the stroke. The time of travel from any oneposition to any other is thus the same regardless of the distance moved.

Another important benefit deriving from the use of a clutch of theaforementioned type, is that the eccentric loading matches the impedanceof the input power source and of the output. At the beginning and end ofa cycle, when the forces are high (and the velocity is low) the pulleyis near top dead-center giving the clutch a large mechanical advantage.At the mid-stroke (when the acceleration is near zero), the mechanicaladvantage is in favor of the cable. The design of the clutch-accordinglybecomes an important factor in the total mechanical selector unit andone type of clutch known as the wrap spring clutch is particularlysuited for this type of service. A preferred form of such wrap springclutch is illustrated in FIGURE 1A; and it will be noted from thesubsequent description that some of the elements comprising this clutchdiffer from conventional wrap spring clutches.

Thus, referring to FIGURE 1A, it will be seen that in accordance withthe present invention, an actuator.

taking the form of a wrap spring clutch may comprise a power shaft 79which is constantly rotated by a motor 71; and an output shaft 72 isdisposed collinear with the power shaft 76 and spaced therefrom. Anouter wrap spring 73 is placed about the power shaft 7% and output shaft72, and the turns of the said spring 73 are divided between the saidoutput shaft and the power shaft. A ratchet 74 (the configuration ofwhich more easily seen in FIGURE 13) is carried by the power shaft 7%and is adapted to be capable of free rotation on the said shaft 79.Spring 73 is coupled at one of its ends to the saidratchet 74, and iscoupled at the other of its ends to output shaft .72.

In the design of the clutch, the diameters of the power shaft 7% andoutput shaft 72 are the same, and the natural internal diameters ofspring 73 is somewhat smaller than the diameters of the shafts 70 and'72. A pulse-responsive interposer or latch is coupled to the ratchet 74and is held in position adjacent the said ratchet 74 by a spring 76whereby,'in the absence of pulse input at terminals 77, the interposer'75 restrains rotation of the ratchet 74. In this condition ofoperation, therefore, the outer'wrap spring 73 is caused to exhibit asome what larger internal diameter than the diameters of shafts 70 and72; and no power is transferred through the spring 73 to the outputshaft '72 from the constantly rotating power shaft 76.

If now a pulse input should appear atterminals 77, the interposer 75will be pulled downward thereby releasing the ratchet 74. The wrapspring-73 will thereupon engage the outer peripheries of power shaft 7%and output shaft 72, and will drive the output shaft forward with atorque equal to where P is the interference pressure, r is the radius ofthe shafts 79 and 72, w is the width of each wrap spring turn, e is thebase of the natural system of logarithms, a is the coefficient offriction, and at is the number of turns of the wrap spring on the powershaft 76 in radians. The pulsed interposer 75 will thereafter'ride uponthe external peripheral surface of the ratchet 74, as at 78 (see FIGURE1B), until the said interposer '75 once more hits a step, such as '79,in the ratchet 74, whereupon the drive spring 73 will once more bedisengaged and the output shaft will cease in its rotation.

Referring to FIGURE 15 for the moment, it will be seen that the steps 79and Si defined by the ratchet 7 are substantially with respect to oneanother, and therefore, when the wrap spring clutch, illustrated inFIGURE 1A, is pulsed, the output shaft 72 will define a 180 turn beforeit is once more caused to stop. During this rotation, a pulley '81eccentrically coupled to the output shaft 72 by an arm 82, will becaused to move through 189 and through a distance corresponding to twicethe eccentricity afforded by arm 82. When the pulley 81 does so move, acable associated with that pulley will have its effective length changedin the manner described, for instance in the said patent to Henschel etal., whereby a work piece or transducer coupled to that cable will movethrough an appropriate distance.

In the particular form of wrap spring clutch shown in FIGURE 1A, asmaller or inner wrap spring 83 is disposed internal of the power shaft70 and output shaft 72-, with the turns of the said spring 83 againbeing divided between the said shafts 79 and 72. The direction ofwinding of spring 83 is opposite to that of drive spring 73; and inpractice, therspring 83 will slip so long as the power shaft 70' isturning faster than the output shaft '72. if, however, the output shaft72 should attempt to turn faster than the power shaft 70, the innerspring 83 engages, thereby preventing the output from going faster thanthe chosen r.p.m. of the power shaft 70.

The stopping tongue for the wrap spring clutch, illustrated anddescribed in reference to FIGURE 1A, is provided by a detent systemcomprising a detent ring 84 carried by the output shaft 82 andcooperating with a pair of detent arms 35. This configuration will bemore readily apparent from an examination of FIGURE 15; and it will beseen that the detent ring 84 preferably includes one or more detentnotches 86"and 87, machined into the said ring 84. The detent notches 86and 87 cooperate with a pair of roller followers 88 and 89 carriedrespectively by the pair of detent arms 85; and the said detent arms 85are pivotally mounted at points 90 and are spring-loaded by a spring 91,whereby the roller followers 88 and 89 are urged toward one another intothe detent notches 86 and 87. When the drive clutch spring 73 (FIGURE1A) is engaged by pulsing of the actuator interposer 75, sufficienttorque is developed to both accelerate the clutch and to drive it out ofits detent position. The output shaft 72 then proceeds to rotate at somespecified r.p.m. defined by motor 71, through substantially 180, in themanner already described; and as this rotation approaches its 180position, the detent rollers 88 and 89 start to descend the detent notchwalls defined by notches 86 and 87. The inner wrap spring 83 'does notallow any over-speed of the output shaft 72, and

the phasing of the rachet notches 79 and 80 with respect to the detentnotches 86 and 87 is such that the interposer 75 contacts itsappropriate step in the ratchet 74 at a time slightly before the detentrollers 88 and 89 reach the bottom of their corresponding detentnotches.

If the energy product of the depth of the detent notch and the springload aiforded by spring 91 is greaterthan the energy contained in therotation of the clutch, the clutch cannot go past its detent position,and is thus trapped. It is of interest to note that since the free endof the drive spring (that is the end of the spring attached to ratchet74) is prevented from rotating from a point prior to the zero positionof the detent notch, the spring 73 is unwrapped from the shafts 70 and72 in a static position,

and this consideration serves to minimize the wear on the wrap spring73.

When it is desired to operate a clutch for a shorter cycle time thanthat already described, and when the stroke of the clutch need not belarge, it is possible to 'clutch to operate through only 90 degrees(rather than through 180 degrees) whereafter clutch rotation is halted,until occurrence of a further control pulse, by the unwrapping of spring73 as well as by a detent system similar to that already described inreference to FIGURES 1A and 113. It should be noted, of course, thatwhen the four-step ratchet 92 is employed, the detent ring (similar to84) should also have four, rather than two, spaced detent notches(similar to 86 and 87).

While the form of wrap spring clutch described in reference to FIGURE 1Ahas one end of the spring 83 connected to the output shaft 72, it shouldbe noted that this is not necessary; and if desired, the said one end ofspring 73 may be coupled to a mass 94 (see FIGURE 1D), rather than tothe shaft 72 itself. This alternative configuration achieves certainappreciable benefits. Thus, the important adjustment in respect to therelationship between the down slope of the detent notch and the detentroller at the moment when the set or step in the ratchet strikes theinterposer, such as 75, is now done automatically and continuously.

If the interposer should strike its appropriate ratchet step before thedetent roller has reached the detent notch, the spring 73 will standstill as the output comes to a stop. Each time the clutch is pulsed, theleading condition of the wrap spring is decreased until the roller fallsinto the detent shortly after the release of the drive spring. It shouldfurther be noted that, if for some reason such as wear, slippage, orinitial adjustment, the opposite condition exists, i.e. the bottom ofthe detent notch leads the step of the ratchet, the action of mass 94rectifies this error over a series of cycles; and each time the clutchstops, the mass 94 causes the spring 73 to unwind and shift forward asmall amount. Over a series of operational cycles, therefore, the detentroller walks its way down the up-slope of the detents and the twoactions then stabilize one another.

Wrap spring clutch actuators, generally of the type described inreference to FIGURES 1A, 1B, 1C and 1D find particular utility in pulleyand cable type selector mechanisms, and a preferred form of selectormechanism utilizing such clutches is illustrated in FIGURE 2. Be foreproceeding with a detailed description of this selector system, however,it should be noted that in a preferred form of the invention, of thetype illustrated in FIGURE 2, the actuator tends to move a carriage 95adjacent an information storage system comprising a magnetic disk-file96 which is rotated by shaft means 97. A basic file, as presentlyutilized, comprises one hundred metal recording or storage disks ofapproximately 18 inches in diameter, stacked on a single shaft with aspacing between adjacent disks of approximately /4 of an inch. Theoverall stack of magnetic storage disks thus has a height of 25 inches.

It has been shown that for a given frequency and a maximum pulsedensity, the most efiicient storage can be accomplished on any one ofthe disks comprising the storage file 96 by using only one-half thediameter of a disk for writing and four and one-half inches of diskradius are accordingly available for this storage and reproduction ofinformation. If we should now assume that the carriage 95 carries atransducer having five channels with a channel spacing of 25 to theinch, then one hundred channels occupy a distance of four inches. Thismeans that the transducer or magnetic head carried by carriage 95 has tomove to twenty distinct positions on each disk comprising the file 96,in order to have access to all the information on that disk; and inorder to simplify head construction, an interlacing scheme is ordinarilyemployed.

As described in the aforementioned application Serial No. 485,746, bothsurfaces of individual disks comprising the file 96 are employed for thereading and writing ofin- Y formation; and the magnetic heads, of whichthere are two carried by carriage 95, are inserted into the spacebetween two adjacent disks, with one head being positioned against thebottom surface of an upper disk, and the other head being positionedadjacent the top surface of a lower disk. The disks, as mentionedpreviously, are rotated by a shaft 97 at 1200 rpm. so that therepetition time for any information item on a given disk is 15milliseconds.

The selector mechanism shown in FIGURE 2 cooperates with a disk file,generally of the type described above, for preselecting disks to beoperated upon, and this selector comprises a clutch bank 98-99. Forpurposes of clarity, the said bank 98-99 has been illustrated as twodistinct clutch'banks, each of which carries four half-revolutionclutches and a pair of fixed pulleys. In a practical embodiment of thepresent invention, clutch bank 99 in fact comprises the opposite side ofclutch bank 98; and a total of four power shafts, extending completelythrough the banks 98- -99, are utilized to drive the eighthalf-revolution clutches coupled to opposing sides of the said bank9899, respectively.

Referring to FIGURE 2 in greater detail, it will be seen that one sideof the clutch bank designated as 98, carries four half-revolutionclutches 100 through 103 inclusive, and a pair of fixed pulleys 104 and105. Similarly. the other side of the clutch bank, designated as 99,carries four further half-revolution clutches 106 through 109 inclusive,and a pair of fixed pulleys 110 and 111. Possible alternative positionsfor the pulleys coupled to half-revolu- 7 tion clutches 1th to 103 and186 through 109, are illustrated in dotted lines in FIGURE 2; but thisparticular dotted representation is not meant to be illustrative of theactual relative throws of the several clutches. To the contrary, and aswill be described subsequently, the throws of the several clutches mayeither equal or difier from one another; and the use of clutches havingdiiferent relative throws is specifically illustrated in FIGURE 3 (to bedescribed), but has not been illustrated in FIG- URE 2 due to theextremely Wide ratio of throws (e.g. as much as 30 tel) preferablyemployed in the arrangement of FIGURE 2. An elongated cable 112 iscoupled to the aforementioned carriage 95' and is caused to passadjacent a fixed pulley 113 into the several pulleys comprising clutchbank 98; and then passes over an end pulley 114 and over the severalpulleys comprising clutch bank 99. The said cable 112is then passedadjacent a further fixed pulley 115, through an overload unit 116 whichserves to selectively protect the cable from excessive tensions producedby the system when the carriage 95 tends to be driven too far orotherwise cannot move when driven; and the said cable 112 then passesover further fixed pulleys 117 and 118 and over movable pulley 119, backto carriage 95. A spring or'compliance member 120 is connected tothepulley 119 and thence to a stable structure, as illustrated, thereby toprovide the desired compliance in the system.

In a preferred embodiment of the present invention, the code-weightingassigned to the several half-revolution clutches comprising the clutchbanks 9899, is such thatthe relative throws of the clutches (asdetermined, for instance, by the eccentric mounting of the pulleysthereon) are 30, 30, 20, 1O, 3, 3, 2, and l; and because of thecontinuity of the cable 112, the eight clutches having theaforementioned relative throws may be positioned as desired on theclutch bank 9899. By utilizing eight clutches having the code-weightingdesignated, the selector mechanism is adapted to move carriage 95through positions zero to ninety-nine (i.e. to any selected one of ahundred discrete positions) adjacent the disk file 96, in response tothe pulsing of appropriate wrap spring clutches comprising the clutchbank 98-99. The function of these relative code-weightings will becomemore apparent'from a consideration of the following.

As mentioned previously, the clutch bank 98-99 comprises 'a total ofeight half-revolution clutches; and the individual clutches are,therefore binary devices having just two positions. The output end ofeach of the clutches carries an eccentric arm, on which is mounted apulley on a bearing; and this structure has already been described inreference to FIGURE 1A. In addition, it will be noted that the clutchesare arranged, as shown in the drawing, to cooperate with a cable, suchas a thin steel cable .112, wound about their respective pulleys; and,as has already been discussed, it is evident that a change in positionof any one clutch will result in either pulling in the cable or lettingout the cable, by an amount equal to twice the total throw of a givenclutch arm.

The aforementioned one hundred discrete positions of carriage 95 may beobtained by actuating a suitable combination of the eight clutches whenthe aforementioned code-weighting is assigned to these clutchesrespectively. Since the disks comprising file 96 are spaced one quarterof an inch apart, a one-unit clutch should have a throw of /8 of aninch; a two-unit clutch should have a throw of A of an inch; athree-unit clutch should have a throwof of an inch, etc. As mentionedpreviously, the eight clutches comprise 'a single one-unit clutch, asingle two-unit clutch, two three-unit clutches, a single ten-unitclutch, a single twenty-unit clutch and two thirty-unit clutches; anddue to the relative throws aliorded by the clutches, the selectiveactuation of appropriate clutches will effect the aforementionedselective positioning of carriage 95 and of the heads carried thereby,through any one of one hundred discrete positions. Since the illustratedform of selector in FEGURE 2 is not a push-pull system, the compliancemeans or spring 12% is provided for providing acceleration in adirection opposite to that afforded by the selector. In other words, thespring 129 provides a pull in one direction while the clutch selectorsystem provides a pull in the other direction.

Examining now the over-all structure shown in PEG- URE 2, with referenceto the discussion already given in reference to FIGURES 1A, 1B and 10,it will be noted that the wrap spring clutch selector system is onegiving a controlled acceleration. Each of the clutches basicallycontributes a modified sinusoidal acceleration to the carriage 95 andthe summation'of these accelerations, which are all of the same period,will be a modified sinusoidal acceleration having a maximum amplitude ofabout 14 Gs (the 14 G fi'gu're being based upon the dimensioned clutchbank actually employed, and being also upon a 200 rpm. shaft speed). Theclutches to be operated are all tripped simultaneously so that theoutput is a summation of the movements provided by individual clutches,and this means that full motion takes place in 150 milliseconds. The 14G figure mentioned above is then required in moving the carriage theinches comprising stack 96 in 150 milliseconds. While this figure may goup to 17 Gs if the clutches are rotated in opposite directions, theimportant thing to note is that the acceleration is a controlled one andprovides very rapid transportation of the carriage 95 with a minimum ofacceleration. To do the same job in the same period of time using asquarewave acceleration, would reduce the acceleration figure by alittle better than percent; but such squarewave acceleration, whileproviding a theoretical optimum if jerk effects are not considered, ismuch more difiicult to accomplish with a practical mechanism.

It should further be noted that the clutches employed are operatedsubstantially as positive engagement clutches, and that it is onlyduring the brief transition period when they are being accelerated up tospeed that any slip occurs. During this period, however, the only loadthat the clutches see is their own inertia load, and this follows sinceat the instant of engagement their motion is at a right angle to theexternal load, i.e. to the cable tension, no matter how high that loadis. Thus, the cable tension does not apply any torque load to the clutchduring the instant of engagement, but acts directly through the centerof the clutch bearing; and it is only after the clutch is actuallyengaged and moving from the vertical position that it starts to see thetorque components of the external load.

It is also important to note that the Wrap spring clutches, when drivingthe load, i.e. when pulling against the spring load as in the case ofgoing from a position zero to a position ninety-nine adjacent disk file96, accelerate the load for approximately half the distance, after whichtime the spring is serving to decelerate the load. The return spring 120therefore has to be strong enough to insure the full deceleration of theload, and to maintain some necessary tension in the system at all times.

When the carriage is going in the opposite direction, that is let us sayfrom a position ninety-nine to a position zero adjacent disk file 96,the spring serves to accelerate the load while the clutch bank pays outcable. Now, since the clutches can only act in the opposite direction tothe direction of the loads, this means that there is an overhauling loadin this particular case, i.e.

the spring might tend to accelerate the output faster than the clutch isactually paying out cable. The clutch would then tend to override itsdrive shaft and would have an uncontrolled acceleration; but thisoperation is effectively prevented by the internal anti-overrunning wrapspring 83, described in reference to FIGURE 1A.

. within a selection device, and need not move.

Thus, the design of the clutches is such that they again control theacceleration and deceleration in the reverse direction.

It should further be noted that due to the provision of the detent ringand detent arm and followers, described in reference to FIGURE 1B, theover-all system operates to position the carriage with substantiallyshockless deceleration, whereby noise, shock and wear in the system aresubstantially reduced.

While particular forms of selector mechanisms have been described, itshould be stressed that the function of the selector is not to positionthe carriage or the heads carried thereby with extremely great accuracy,but serves to position the said carriage within'relatively small limits,which may be further limited through the provision of a rack with fixedstops. Thus, the selector shown in FIGURE 2, for instance, will serve toposition carriage 95 very rapidly, that is in 150 milliseconds, to anapproximate desired position, for instance withinone-half of thedistance separating two adjacent disks comprising file 96. The systemmay be so arranged that the carriage will'over-shoot by approximatelythis one-half. separation distance, and a latch can be thrown in thecarriage whereby the said carriage latch may 1 be lowered onto the rackstop.

It will be appreciated that the selector mechanism described inreference to FIGURE 2 moves a workpiece in a single direction withrespect to a stationary reference structure. In practice, however, it isoften desired to selectively position such a work piece within a movingsystem; and in this respect it is further desirable that the selectormechanism be substantially independent of the moving system. Thus,referring to the aforementioned copending application, Serial No.485,746, the moving system may comprise a disk-type memory which may beselectively translated in a first plane thereby to preselect aparticular storage surface for operation thereon. In such a disk-typememory system, the magnetic transducer operating on the disk memory isthen required to be translated to a desired location on the preselecteddisk. It will be noted that the structure thus presented embodiesmovement in directions substantially orthogonal to one another; and inorder to permit the work piece or transducer to be selectivelypositioned within such a moving system, a form of differential selectormust be provided. One possible such arrangement has been illustrated inFIGURE 3.

Thus, a selector mechanism 40 may comprise a first plurality ofstationary pulleys 41 through 44 inclusive and a second plurality ofmovable pulleys 45 through 47 inclusive, the said movable pulleys beingselectively displaced by actuators '48 through 50 inclusive, under thecontrol of signal inputs thereto. The selector mechanism 40 is thusidentical in construction and operation with the selector of FIGURE 2,and it will be noted that the said selector mechanism 40 may be fixedlypositioned The over-all system may further comprise a movable structure51, corresponding for instance to the carriage 95 of FIGURE 2, and thesaid carriage 51 rides on tracks 52 and is capable of translationhorizontally through the agency of acable 53 coupled to fixed pulleys54. As

ihas .been'mentioned previously, the moving system 51 or'95 may take theform of a carriage for a disk-type memory, and horizontal movement maybe effected by a. cable under the control, for instance, of a separatevia pulleys 58--and--59 to -a point-60-on the workpiece 75.,may beelimina ted.

55; while the other end 61 of the cable 57 may be coupled via a pulley62 to a point 63 on the movable system 51 or 95. A further cable 64 maybe coupled between a point 65 on the work piece 55 and a point 66 on themoving system 51 or 95, via the several pulleys 6711 through 67ainclusive. A compliance device 68, which may comprise a spring, may becoupled between pulley 67a and a stationary reference structure 69, asshown. It will be appreciated that the several pulleys 58, 59, 62, and67a through 67s, are provided for convenience only, and that otherarrangements may be employed to accomplish the purposes of the presentinvention.

The difierential selector system thus. illustrated in FIGURE 3 comprisesa movable. work station'and a work piece selectively capable ofdisplacement at right angles to the direction of movement of the saidstation. The system further comprises a first cable networkcouemployed," coupled at one of'its ends to the movable system andcoupled at the other of its ends to the said "work piece; and thisfurther cable network may include the compliance means 68, as shown.

Referring to FIGURE 3, it will be seen that motion of the moving system51 or 95 will not affect the tension on cable 57 or the tension at theends 56 and 61 of the said cable 57 inasmuch as cable 57 will merely runover idler pulleys 41 through 44, 58, 59 and 62, and over the actuatingpulleys 45 through 47, during translation of the moving system 51 or 95.Should it be desired, however, to alter the position of work piece 55,within the moving system 51 or 95, then selective actuation of the inputlines to the selector mechanism 40 will cause relative motion of theindividual selector pulleys 45, 46 and 47, thereby to'cause a relativeshortening or lengthening of the cables 57 and 64 so as to causerelative motion between the ends 56 and 61 of the said cable 57. Suchrelative motion will move transducer or work piece 55 in the mannerdescribed, and this movement will operate against the compliance means68 of the tensioning system composed of tension cable 64 and the pulleysassociated therewith. Removal of signal inputs to the actuators 48through inclusive will similarly allow the work piece to move in anopposite direction so as to relax the tensioning system comprising cable64, its associated pulleys and compliance means 68.

It will thus be seen that signal inputs to the selector mechanism 40will position the work piece 55 to one of a plurality of independentlocations within the moving system 51 or 95, and this positioning willbe efifected regardless of the arbitrary position of moving system;

tively heavy, rugged and massive selector mechanism to be positionedexternally of a moving system and to so operate on said moving systemthat members therein may be suitably adjusted or positioned. As aresult, the actual portions of the system providing selection andrelative or difierential movement, are not affected by the mass of theselector mechanism itself, whereby high speed operation may be attained.

It should be noted that the tensioning system comprising cable 64,pulleys 67a through 67:? inclusive, and

compliance means 68, has been provided merely to relieve moving system51 or of the additional weight or mass of compliance means 68- IfthisIweight. or 0 mass factor is not important in operation of theoverallsystem, the compliance means 68 may be incorporated directly intothe said moving system and may comprise,

for instance, a spring connected directly between points 65 and 66whereby cable 64 and its associated pulleys While preferred embodimentsof the present invention have been described, it will be appreciatedthat many variations will be suggested to those skilled in the art, inaccordance with the principles discussed. The foregoing description istherefore meant to be illustrative only and is not limitative of ourinvention; and all such variations as are in accord with the principlesdescribed, are meant to fall within the scope of the appended claims.

Having thus described our invention, we claim:

1. In a positioning mechanism, a first movable body, means for movingsaid body in a first reference direction, a second movable body carriedby said first body, selector means for moving said second body in asecond reference direction substantially orthogonal to said firstreference direction, said selector means comprising a cable coupled atone of its ends to said first body and coupled at the other of its endsto said second body so that motion of said first body in said firstreference direction does not cause motion of said second body in saidsecond reference direction, a plurality of non-displaceable idlerpulleys adjacent said cable for establishing a reference location ofsaid cable, and a plurality of signal responsive actuators coupled tosaid cable for selectively moving portions of said cable throughpredetermined displacements with respect to said idler pulleys tothereby move said second body in said second reference direction.

2. The positioning mechanism of claim 1 wherein each. of said actuatorsincludes a wrap spring clutch.

3. Thepositio'ning mechanism of claim 1 wherein each of said actuatorsincludes a signal responsive partial revolution clutch, and a rotatablepulley eccentrically coupled to said clutch and in contact with saidcable.

4. The mechanism of claim 1 wherein said pluralityof actuators comprisesa plurality of displaceable pulleys disposed intermediate said idlerpulleys respectively, said cable being carried both by said displaceablepulleys and 'by said idler pulleys, and wrap spring clutch means coupledto said displaceable pulleys for selectively altering the positions ofsaid displaceable pulleys with respect to the positions of said idlerpulleys.

S. The mechanism of claim 4 wherein said wrap spring clutch meansdisplace difierent ones of said displaceable pulleys through differentphysical distances, respectively, in response to signal inputs appliedto said clutch means.

6. The mechanism of claim 1 including resilient means disposed betweensaid first and second bodies for imposing a predetermined, referencetension on said elongated cable.

7. The mechanism of claim 6 wherein said resilient means comprises aspring.

8. The mechanism of claim '6 wherein said resilient means comprises afurther cable coupled at one of its ends to said first body and coupledat the other of its ends to said second body, a reference structure, andspring means disposed between said further cable and said referencestructure.

9. The mechanism of claim 1 wherein said first movable body comprises acarriage movable with respect to an information storage device, saidsecond movable body comprising an information transducer disposed onsaid carriage for movement adjacent said storage device.

'10. A selector mechanism comprising an elongated cable, a firstplurality of pulleys carrying said cable, a second plurality of pulleyscarrying said cable, a plurality of signal responsive actuators forefiecting predetermined relative displacements between pulleys of saidfirst and second pluralities thereby to selectively change the positionsof opposite ends of said elongated cable relative to one another, aninformation storage device, a carriage, transducer means carried by saidcable and by said carriage adjacent said storage device, whereby therelative position between said storage device and said transducer meansis varied in responseto signals applied to said actuatom, and means forselectively moving said carriage in a first reference direction, withrespect to said storage device said selector mechanism moving saidtransducer means in a second reference direction substantiallyorthogonal to said first reference direction.

11. A selector mechanism comprising an elongated cable, a plurality ofrotatable pulley devices carrying said cable, a work piece coupled tosaid cable, means for applyspring adjacent both said power shaft andsaid output shaft, a ratchet, said spring being coupled at one of itsends to said ratchet, driving means coupled to said power shaft, anda-signal responsive latch coupled to said ratchet, whereby said latchmay be selectively actuated thereby to effect a power transfer from saiddriving means and power shaft to said output shaft viasaid spring.

v 13. The mechanism .of'claim 12 wherein each of said clutches includesa further spring adjacent both said power shaft and saidoutput shaft,said further spring being adapted to engage said power shaft and outputshaft only when the speed of rotation of said output shaft tends toexceed that of said power shaft, thereby to prevent overrunning of saidoutput shaft.

14. The mechanism of claim 11 wherein each of said clutches includes a.power shaft and an output shaft, and

an arm attached to the longitudinal axis of said output shaftsubstantially orthogonal thereto, said pulley devices beingcoupledrespectively to said arms at points spaced from the longitudinal.axis of said output shaft.

15. The mechanism of claim '14 wherein different ones of said pulleysare'differently spaced from their respective output shaft whereby saidwork piece is moved different "distances in response'to actuation ofdifierent ones of said clutches.

16. In a selector mechanism, a wrap spring clutch having a power shaft,an output shaft, and a spring for selectively coupling said power shaftto said output shaft, means for rotating said power shaft, pulseresponsive means for causing said spring to transfer the rotation ofsaid power shaft to said output shaft, a pulley connected to said outputshaft with'th'e pulley axis at a position displaced from the axialcenter of said output shaft whereby rotation of said output shaftchanges the position of said pulley, a cable carried by said pulley, anda work piece connected to said cable whereby changes in position of saidpulley are coupled through said cable to said work piece thereby tochange the position of said work piece.

17. In an information storage system of the type having a plurality ofrotatable recording disks arranged in series and adapted to becontinuously rotated, and a transducer device movable in a firstdirection with respect to said disks to be positioned adjacent aselected one of said disks and movable in a second direction transverseto said first direction thereby to be positioned adjacent a certainportion of the selected disk, the combination therewith of a mechanismfor positioning said transducer device, said mechanism comprising acarriage, first cable means connected to move said carriage in saidfirst direction, first actuator means responsive to certain inputsignals for producing .a certain displacement of said first cable meansin said first direction, said transducer being supported on saidcarriage for movement in said second direction, second cable meansconnectedto said transducer for producing movement of said transducer insaid transverse direction with respect to said carriage, and secondactuator means responsive to certain input signals for producing acertain displacement of said second cable means in said transversedirection, whereby said transducer may bemoved in said two'directions.

18. In an information storage system of the type having a plurality ofrotatable recording disks arranged in series and adapted to becontinuously rotated, and a transducer device movable in a firstdirection with respect to said disks to be positioned adjacent aselected one of said disks and movable in a second direction transversedto said first direction thereby to be positioned adjacent a certainportion of the selected disk, the combination therewith of a mechanismfor positioning said transducer device, said mechanism comprising acarriage, first cable means connected to move said carriage in saidfirst direction, first actuator means responsive to certain inputsignals for producin a certain displacement of said first cable means insaid first direction, said transducer being supported on said carriagefor movement in said second direction, second cable means connected tosaid transducer and to said carriage for producing movement of saidtransducer in said transverse direction with respect to said carriageand without regard to the position of said carriage, and second actuatormeans responsive to certain input signals for producing a certaindisplacement of said second cable means in said transverse direction.

19. In an information storage system of the type having a plurality ofrotatable recording disks arranged in series and a transducer devicemovable in a first direction with respect to said disks to be positionedadjacent a selected one of said disks and movable in a second transversedirection to be positioned adjacent a certain portion of the selecteddisk, the combination therewith of a mechanism for positioning saidtransducer device, said mechanism comprising a carriage, first cablemeans connected to move said carriage in said first direction, firstactuator means responsive to certain input signals for producing acertain displacement of said first cable means in said first direction,said transducer being supported on said carriage for movement in saidsecond direction, second cable means connected to said transducer forproducing movement of said transducer in said transverse direction withrespect to said carriage, and second actuator means responsive tocertain input signals for producing a certain displacement of saidsecond cable means in said transverse direction, said first and secondactuator means including different pluralities of pulleys mounted forSwinging about eccentric axes for producing various displacements ofsaid cables.

20. In a positioning mechanism, a first body movable with respect to areference, a second body mounted for movement with said first body andwith respect thereto, resilient means for yieldably biasing said secondbody toward a certain position with respect to said first body, a cablehaving one portion connected to said first body and another portionconnected to said second body, means for guiding said cable for movementin a path having a predetermined relation to said reference, an actuatoroperable on a portion of said guiding means for selectively moving saidcable thereby to move said second body from said certain position,whereby said second body can be selectively moved by said actuator todifierent positions with respect to said first body.

21. In a positioning mechanism, a first body movable with respect to areference, a second body movable with respect to said reference and tosaid first body, means effecting relative motion both between each ofsaid first and second movable bodies and between said second body andsaid reference, said motion effecting means comprising means for movingsaid first body with respect to said reference, a cable coupled at oneof its ends to said first body and coupled at the other of its ends tosaid second body, and a plurality of actuators coupled to said cable,each of said actuators being responsive to a predetermined input signalfor imposing a predetermined displacement of said cable with respect tosaid reference, each of said actuators thereby producing a displacementof said first body with respect to said second body of difierentmagnitude without afiecting the position of said first body with respectto said reference.

22. The mechanism of claim 21 wherein each of said actuators comprises amovable pulley device, and a signal responsive clutch eccentricallycoupled to said pulley device.

23. The mechanism of claim 22 wherein each of said clutches comprises ahalf-revolution wrap spring clutch.

References Cited in the file of this patent UNITED STATES PATENTS843,508 White Feb. 5, 1907 1,139,972 Henschel et al. May 18, 19151,481,153 Rosendahl Jan. 15, 1924 1,807,035 Herman May 26, 19312,004,650 Collyear et al June 11, 1935 2,053,580 Racklyeft Sept. 8, 19362,098,021 Wheeler 'Nov. 2, 1937 2,161,941 Zapp June 13, 1939 2,298,970Russell Oct. 13, 1942 2,301,908 Wilcox Nov. 10, 1942 2,358,094 PanishSept. 12, 1944 2,411,055 Rich Nov. 12, 1946 2,475,432 Marihart July 5,1949 2,511,349 Klay June 13, 1950 2,519,725 White Aug. 22, 19502,582,987 Hagenbook Jan. 22, 1952 2,620,389 Potter Dec. 2, 19522,674,728 Potter Apr. 6, 1954 2,690,913 Rabinow Oct. 5, 1954 2,733,425Williams Jan. 31, 1956 2,837,046 Carson et a1. June 3, 1958 2,847,859Lynott Aug. 19, 1958

